The present invention relates to wood heaters with a mechanism by which the enclosed fire may be selectively viewed.
Open hearth fireplaces are aesthetically appealing but are ineffective sources of primary or secondary heat. Wood heaters that allow controlled ventilation to the fire are much more effective if not pleasing in appearance. It therefore becomes desirable to provide some form of wood heater that presents the capability of heating effectively as a wood stove yet allows selective viewing of the fire.
Various unsuccessful attempts have been made to combine the aesthetic appeal of the fireplace with the higher heating efficiency of "air-tight" wood stoves.
Many attempts have resulted in the unattractive freestanding fireplaces with removable metal or glass doors. Such apparatus do not include effective heat exchange capabilities or effective damper or draft arrangements.
U.S. Pat. No. 3,757,766 to Robert L. Stevenson discloses a wood heater with a viewing window and enclosed collapsible door that is adapted to open or close, with the closed position shielding the window from the interior of the adjacent firebox. The collapsible door is operated by control knobs that are found behind exterior doors at opposite ends of the window housing. The controls include knobs that slide within inverted L-shaped slots formed through the window housing. These open slots are found behind access doors mounted at opposite ends of the window housing. The doors selectively close so an undesired draft is not produced through the open slots. A ventilator is positioned along a top side of the window housing that is also selectively closed by a door structure. There is no provision for guiding the ventilation air other than the shape or position of the slot itself. The firebox is substantially cylindrical and has no provision for heat exchange other than by natural convection.
The "Thermo-Blaze" fireplace heating systems sold by Gorich Associates, Inc. of Brockton, Mass. is a combination fireplace-heater that is similar to the Stevenson unit. The "Thermo-Blaze", however, has a "roll-top" door that selectively seals the viewing window from the fire. In addition, a shroud is provided partially about the back and top surfaces of the cylindrical firebox for the purpose of guiding air directed from a blower unit. The air is circulated over the heated surface of the firebox and is exhausted forwardly of the firebox unit.
With both of the above heaters, heat is conducted through the window housing directly to the window pane. Glass can be broken or cracked when the viewing doors are closed with no ventilating air being allowed to circulate over the glass. Heat is conducted through the housing and radiated from the viewing doors against the glass and can eventually cause damage or breakage, especially when fires are "banked" to last through the night.